The present invention relates to a vibratory screening apparatus which improves the removal of solids from liquid and reduces screen plugging. A pair of screens is held in superimposed abutting relationship. The first screen has rectangular openings of first and second dimensions. The second screen has rectangular openings of third and fourth dimensions perpendicular to the first screen openings with the third dimension being larger than the first dimension of the first screen; and the fourth dimension being smaller than the second dimension of the first screen. Solids that will tend to plug the first screen opening will be rejected by the second screen wires positioned below. A third screen of coarser mesh may be placed beneath the first and second screens to underlie and support them. The screens are coupled to a vibratory source.
It is necessary in many applications to separate solids or finely divided materials from a liquid composition. Industrial screening equipment exists for this purpose. A major concern in this art, however, is the tendencey of the screening equipment to become clogged or plugged when separating finely divided solids from liquids. This clogging of the screens greatly impairs the effectiveness of industrial screening equipment, and in some cases the effectiveness of such equipment may be essentially reduced to zero. Various methods have been proposed to remove solid particles wedged into industrial screening equipment such as the use of square openings in both screens with the bottom screen; however, plugging of the screen still occurs.
Other applications in the art set forth a vibratory screening apparatus comprising a plurality of screens in immediate vertical juxtaposition with the mesh size of the screen cloths varying from screen to screen and the screens are enframed and coupled to a vibratory source. Clogging or plugging is still a problem in this case, however.
Rectangular mesh screens are less susceptible to plugging than square; however, larger particles can pass through a rectangular screen than a comparable square mesh. It has been discovered that by using a square mesh screen under the rectangular screen, the square openings being larger than the smaller dimension of the rectangular opening and smaller than the larger dimension, solids that would tend to plug the rectangular opening would be rejected by the square mesh wires below. The rejection of larger particles by the wire below would also improve the separation capabilities of the rectangular mesh making its particle rejection cut point comparable to an equivalent square mesh.
The instant invention comprises a vibratory screening apparatus which utilizes a pair of screens of specific mesh dimensions held in superimposed abutting relationship. The first screen openings have first and second rectangular dimensions, and the second screen openings have third and fourth rectangular dimensions which are perpendicular to the first screen openings. The third dimension of said second screen opening is parallel to and larger than the first dimension of the first screen opening, and the fourth dimension of the second screen opening is parallel to and smaller than the second dimension of the first screen opening. The screens are then coupled to a vibratory source for vibrating the screens. This design improves the removal of finely divided solids and particulate matter from liquids, by reducing plugging and clogging of the screens.